1. Field of the Invention
The present invention relates to a fan for moving air or for transporting loose material.
2. Description of the Prior Art
The wood-processing industry, in particular, uses fans that suck up the chips, dust and sawdust produced during operations at the workplace and then deliver this debris through separators and into silos. Very often, several such suction evacuation systems are connected to one fan. Before the mixture of air, chips, and/or sawdust is passed through the actual fan, it goes through a separator, within which the larger--and in particular the heavier--particles are removed by gravity.
The present invention relates to a fan for moving air or for transporting loose material, this having a fan-blade wheel, a drive motor, and a suction inlet pipe. Fans of this kind are known. They operate as centrifugal fans, in that the air or mixture that is drawn in enters the fan in an axial direction relative to the axis of the fan blade, is deflected and accelerated radially, and then the air or the loose material that is carried by it is thrown out of the fan in a tangential direction. Such fans have been used for many years, in particular as transport fans used, for example, for hay, as well as in the wood-processing industry. A second disadvantage in such fans is the fact that any possible larger solid particles that are not removed by the separator are accelerated very greatly both radially and tangentially after entering the fan and, as a consequence of this, strike the walls of the outlet pipe like projectiles. Thus, there is a large amount of wear on such material, caused by the abrasive effect of this impact, and in some older plant this even causes deformation of the walls. In the most extreme cases, the walls can even become perforated.
Consideration has also been given to replacing centrifugal fans by other types, such as axial fans. However, such considerations always migrated away from the ideal of using an axial fan. On the other hand, installing a motor in the pipe results in a considerable reduction of cross-section; on the other hand, a motor that is incorporated in this way is always exposed to the impact of solid particles and is thus endangered by such blows. On the other hand, too, such a fan presents a trap for material such that, in the worst case, this can lead to the fan becoming blocked. A further disadvantage of a motor that is incorporated axially in the pipe lies in the fact that it is very inacessible for maintenance and repair operations.